As far as qualifying for Boston w/a walk/run--not too likely. Here is a link to Boston qualifying standards. Qualifying

Unless you're really going to become a serious runner and devote a lot of time and energy to it, it's not likely you'll be going to Boston as a qualified runner. However, if you still really want to run Boston, look into doing it as a "charity runner." Boston always reserves a number of slots for those who raise a given amount of money for specific charities, and this might be a better bet for you if you really want to go to Boston but are not sure you can even run a marathon, let alone a fast enough one to qualify.

dallytante: honeypig beat me to it, but Jeff Galloway is arguably the top walk-run strategy coach out there.

As for your goal, what's your athletic background? I ask because although the advice offered above about running for a year or two before completing a marathon is sound overall it can certainly be done if you have an adequate athletic base.

I say this from experience; I've always been an active guy but never much of a runner prior to completing my first marathon. However, I used a six-month plan, plus an additional couple of months tacked on the front to allow me to get base fitness. I'll be honest and admit I had a conservative finish time of four hours for my first marathon, which I didn't quite achieve. However, I still felt capable and my body held together alright in the end and I finished the race with no problems.

The only caution I would throw out there is your potentially steep goal of qualifying for Boston right away. Some people do it, of course, but assuming you do not have much of a running pedigree doing so will be quite a challenge.

That said, people run sub-three-hour marathons using the walk-run strategy so don't worry about your racing strategy. Just ensure you have the ability to handle the load of the Boston qualifying pace.